I have a March 2011 Cmax with a 1600 cc 115 ps Duratorq diesel. 9600 miles. ie not yet fully run in.

I have reduced power (say 20 - 30%) when laden / up hills / overtaking. c 2200 - 2500 revs in 4th gear. Perhaps tellingly, if I change UP to 5th (revs reduced to 1500) the power is OK!!

The 2 main dealer finds no fault code & have updated the ECU software coding to the latest version but this has not resolved the above. (it did resolve another issue)

I note the following engine characteristic - might this boost be malfunctioning?

""The 1.6-litre Duratorq TDCi is available in a 115 PS power rating. This can deliver extra performance when hard acceleration is required. It does this with an overboost, which increases peak torque from 270 Nm to 285 Nm for up to 15 seconds""

It smacks to me of being a fuel supply issue / software issue. Its not a blocked DPF cat or mass airflow meter.

Needless to say the main dealers are not very interested or seemingly knowledgeable. To them the car runs OK and as long as it is driveable they are happy to see the car leave the garage. But poor performance at these revs is actually potentially dangerous - I have to change down to overtake on the flat, and avoid overtaking going up hills.

Any help would be gratefully appreciated

Regards

Phil Coates